Friday, 27 January 2012

Potatoes neither like nor dislike lime.

I think that it is safe to say that potatoes do not have emotions. They neither like nor dislike lime.

The addition of lime to a potato bed seems to be associated with potatoes getting scab. Scab is a raised unsightly blemish on the potato skin. Streptomyces scabies seems to be the organism that produces scab and this appears to live in more alkaline soils. Lime makes soil more alkaline (raises the pH).

These organisms, that resemble fungi, only infect the surface skin of the potatoes and do not grow into the centre. So I eat potatoes infected by Streptomyces scabies and have done so for years. Most of the time I peel off the outer skin of potatoes anyway. I tend to avoid the scabby ones when making baked potatoes.

The most that can be said about growing potatoes in soil with a relatively low pH is that the skins will probably be more smooth and "shop like". The taste will be exactly the same as potatoes growing in a soil that has a relatively high pH. I don't think that scab overtly alters the size and quality of the potato.

If you are growing for exhibition then the state of the potato skin is important and a low soil pH would be essential but how many of us are exhibition growers?